ACR States

There are five potential ACR states:

When a port’s ACR state is normal, phase tracking, or frequency tracking, the recovered ACR clock is considered a qualified reference source for the SSU. If this reference source is being used, then transitions between any of these three states do not affect SSU operation.

When a port’s ACR state is free-run or holdover, the recovered ACR clock is disqualified as a reference source for the SSU. If this reference source is being used, then transitions to either of these two states cause the SSU to drop the reference and switch to the next highest prioritized reference source. This can potentially be SSU holdover.

Parent topic: Adaptive Clock Recovery (ACR)